Method of preventing breaks on paper machines



Patented Sept. 1, I933.

PATENT OFFICE HAROLD ROBERT RAFTON, OF LAWRENCE, MASSACHUSETTS, ASSIGNOR TO RAFFOLD PROCESS CORPORATION, A CORPORATION OF MASSACHUSETTS METHOD OF PREVENTING BREAKS ON PAPER MACHINES No Drawing.

This invention relates to the manufacture of paper and more particularly to a method of preventing breaks on paper machines.

The principal object of my invention is greatly to decrease if not substantially eliminate the breaks in the web of paper being made from a furnish containing an alkaline filler, and thereby to increase the production of paper by the paper machine.

A further object of my invention is to prevent the formation of soft lumps in a papermaking furnish containing an alkaline filler, such soft lumps tending to cause breaks in the paper web with'the consequent loss of production on the paper machine.

Another object of my invention is to produce paper filled with alkaline filler which is substantially free from lumps and lump spots.

Other objects and advantages of my invention will become apparent during the course of the following description.

In the production of paper as ordinarily carried out, the ingredients used in the furnish are added in suitable proportions to a beater or similar machine, and commonly comprise fibrous material, filler, size, alum, coloring matter and broke. Even in those cases where the paper to be made is substantially unsized, a small amount of size, and less than the amount which would produce a substantial degree of sizing in the paper, is usually employed to better machine operating conditions. The broke mentioned herein is imperfect or waste paper from the manufacture of either coated or uncoated paper.v

In those mills where in addition to ordinary uncoated paper, coated paper is made it is customary to use the coated broke as one of the constituents of the furnish. In some mills the coated broke may be added as dry furnished fed directly to the heater, or, as when the coating is so water resistant that the coated broke cannot be properly disintegrated in the beater, it may be disintegrated in a separate machine, such as a breaker, and then added to the furnish in Wet form, or as slush. In some mills it is customary to add the coated broke to the breaker, and to disintegrate it, using steam Serial No.- 325,406.

if necessary. The disintegrated coated broke may then be furnished to the beater as slush stock either alone or with any other slush stock such as soda, sulphite, old paper stock, or broke from uncoated paper.

Any of these procedures for handling the coated broke are satisfactory when fillers of a non-alkaline character are employed, as clay,'for instance. With such furnishes little trouble is usually experienced with breaks caused by soft lumps forming the furnish.

However, particularly in the production of substantially unsized paper, when the filler employed is alkaline tiller which prevents the customary use of rosin. size, soft lumps appear at the wet end of the paper machine causing breaks in the paper Web which se riously reduce production. This is particularly the case where old paper stock is used as one of the ingredients of the furnish. When this difliculty was encountered there was nothing in the papermaking art to teach the paper technologist or the practical paper maker how to overcome the difficulty or to determine to what factors the lumps were due. Ordinary changes in machine operation such as regulation of the suction at the suction boxes and couch roll, the pressure at the press rolls' and the processing of the stock at the jordan or at the heaters, and the use of sterilizing or preserving agents such as chlorine'or formaldehyde, although perhaps influencing to a limited degree the number of lumps formed, did not greatly reduce these lumps and the breaks therefrom. The ends of the paper Where the breaks had occurred showed that the breaks were due to soft lumps, yet nothing was apparent to shoW what caused the formation of the lumps.

Rosin size with alum used in the beater furnish with the alkaline filler did not reduce the soft lumps and furthermore caused so much foaming on the machine-as to make its use commercially unfeasible.

Thus, prior to my invention there was no method for preventing the formation of soft lumps and the consequent breaks on the paper machine.

I have discovered that the lumps are produced subsequent to the passage of stock through the paper machine screens; that they collect primarily on the under surfaces of those parts of the paper machine inlet and headbox exposed to the flow of the stock; that the lumps contain a higher percentage of nitrogeneous matter than the paper stock from which they are formed; and that the ratio of clay to alkaline filler is higher in the lumps than in the paper mix flowing through the screens from which the lumps are formed. I also have discovered that the principal" source of nitrogeneous matter is the casein used as an adhesive in coated paper. The source of the clay is the filler in the old paper stock which has not been removed in the deinking process. It is prob able that the casein acts as a flotation agent which selectively floats the clay preferentially to the alkaline filler, and that these flotation segregations, combined necessarily with more or less adhering fibre, cause the lumps. I deduced therefrom, that the diminution or substantial removal of casein (derived from the coated broke) from the furnish would remove the flotation agent and thereby remove the chief cause of the lumps. This I found to be the case, namely that the substantial elimination of coated broke from the furnish containing fibrous material including old paper stock, and alkaline filler resulted in a substantial decrease in the lumps formed, and the subsequent substantial decrease in the paper machine breaks, which greatly improved machine operation and increased machine production.

It is possible that formerly the precipitation of the rosin size-alum compound, or even its mere presence may have overcome any flotation difficulty due to the mutual presence of casein and clay, but with the use of alkaline filler, the employment of rosin size was rendered ,unfeasible, and thus the practical solution of the soft lump difficulty proved to be ghe elimination of the casein from the furms In the preferred practice of my invention I eliminate, or substantially diminish, the source of the casein, i. e. the amount of coated broke which formerly was customarily used in similar furnishes prior to my invention. Starch may be used in the furnish if desired.

In a mill having an old paper plant, there is necessarily some coated paper included in the old magazines processed, and although part of this casein is removed, a certain amount remains in the old paper stock. This amount can be reduced by adequate washing of the old paper stock, but there is normally always a small residual amount of nitrogeneous matter remaining in the stock. Similarly there is a small amount of nitrogeneous matter present in the circulating mill waters, but I have found that if the coated broke is substantially eliminated from the furnish of the papers filled with alkaline filler, the small amounts of casein coming from the other sources are ordinarily not sufiicient seriously to interfere with machine operation.

On the other hand, however, the employment of so-called washed coated broke such as is used in some mills, and which is obtained usually by attempting to remove the coating constituents from the coated broke, isnot suitable for use,because the methods of removal ordinarily employed leave suflicient casein present in the stock to give trouble by lump formation.

It will be apparent that my invention is a distinct contribution to the papermaking art in that it teaches how a furnish containing alkaline filler and old paper stock can be run without dilficulty from lumps by those mills which have normally employed coated broke as an ingredient of their furnishes.

Where I use the term alkaline filler, I mean substantially water insoluble filler which when agitated in contact with freshly boiled distilled water, say for an hour, will impart a pH value to such water greater than 7.0, that is, which will be on the alkaline side of the neutral point. Among the fillers included in this group may be mentioned calcium carbonate, of which lime mud from the causticizing process is one form; calcium carbonate magnesium basic carbonate employed in the paper disclosed in my U. S. Patent No. 1,595,416, issued August 10, 1926; calcium carbonate magnesium hydroxide disclosed in my U. S. Patent N 0. 1,415,391, issued May 9, 1922; and other substantially water insoluble normal or basic carbonates of alkaline earth metals (which expression is herein intended to include magnesium), or compounds, double salts, or physically associated mixtures of these with one or more other acid soluble materials of a substantially water insoluble nature.

By the term alkaline filler I also intend to include fibrous material and/or other material such as paper coating constituents or the like containing one or more compounds of the character referred to, such as old papers or similar papers, broke or the like.

For use in the practice of my process, however, these materials should be substantially free from flotation agents such as casein or the like.

When I use the word paper herein, I use 'it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Fourdrinier, cylinder, or other forming, felting, shaping or molding machine.

there I use the word casein herein I use Where I use the expression soft lumps 1 mean lumps which have their origin subsequent to the screening of the stock, being formed in the head box, inlet or the like. These'lumps are entirely different, and easily distinguishable by practical paper makers from slime, i. e. masses of stock usually fermented or decomposed which settle or form hours after the head box and inlet have been regard to any theory contained herein.

While I have described in detail the preferred embodiment of my invention, it is to be 1 understood that the details of procedure may be varied without departing from the spirit of my invention or the scope of the subjomed claims.

I claim:

1. In the manufacture of paper filled with alkaline filler, the improvement in a method of running a furnish containing alkaline filler and fibrous material including old paper stock wher'ebythe formation of: soft lumps is substantially avoided which comprises including in the furnish only stock which is substantially free from flotation agent.

2. In the manufacture of paper filled with alkaline filler, the improvement in a method of running a furnish containing alkaline filler including old paper stock having clay associated therewith whereby the formation of soft lumps is substantially avoided which comprises including in the furnish only stock which is substantially free from agent.

3. In the manufacture of paper filled with alkaline filler, the improvement in a method of running a furnish containin alkaline filler and fibrous material including old paper stock whereby the formation of soft lumps'is Substantially avoided which comprises including in the furnish only stock which is substantially free from nitrogeneous material.

4. Inrthe manufacture of paper filled with alkaline filler the improvement in a method of running a furnish containing alkaline fill er and fibrous material including old paper stock whereby the formation of soft lumps is substantially avoided which comprises including in the furnish only stock which is substantially free from casein.

5. In the manufacture of paper filled with flotation alkaline filler, the improvement in a method of running a furnish containing alkaline filler and fibrous material including old paper stock whereby the formation of soft lumps is substantially avoided which comprises including in the furnish only stock which is substantially free from casein-containing coated broke.

' 6. In the manufacture of paper filled with alkaline filler, the improvement in a method of running a furnish containing alkaline filler, comprising calcium carbonate, and fibrous material including old paper stock whereby the formation of soft lumps is substantially avoided which comprises including in the furnish only stock which is substantially free from casein-containing coated broke.

7. In the manufacture of paper filled with alkaline filler, the improvement in a method of running a furnish containing alkaline filler, comprising calcium carbonate and magnesium compound, and fibrous materialineluding old paper stock whereby the formation ofsoft lumps is substantially avoided which comprises including in the furnish only stock which is substantially free from caseincontaining coated broke.

8. In the manufacture of paper filled with alkaline filler, the improvement in a method of running a furnish containing alkaline filler, comprising calcium carbonate magnesium hydroxide, and fibrous material including old paper stock whereby the formation of soft lumps is substantially avoided which comprises including in the furnish only stock which is substantially free from casein-containing coated broke.

In testimony whereof I afiix my signature.

HAROLD ROBERT RAFTON. 

